Ti3+ Self-Doped Dark Rutile TiO2 Ultrafine Nanorods with Durable High-Rate Capability for Lithium-Ion Batteries

Abstract

Dark-colored rutile TiO<inf>2</inf> nanorods doped by electroconducting Ti³⁺ have been obtained uniformly with an average diameter of ≈7 nm, and have been first utilized as anodes in lithium-ion batteries. They deliver a high reversible specific capacity of 185.7 mAh g^-1 at 0.2 C (33.6 mA g^-1) and maintain 92.1 mAh g^-1 after 1000 cycles at an extremely high rate 50 C with an outstanding retention of 98.4%. Notably, the coulombic efficiency of Ti³⁺-TiO<inf>2</inf> has been improved by approximately 10% compared with that of pristine rutile TiO<inf>2</inf>, which can be mainly attributed to its prompt electron transfer because of the introduction of Ti³⁺. Again the synergetic merits are noticed when the promoted electronic conductivity is combined with a shortened Li⁺ diffusion length resulting from the ultrafine nanorod structure, giving rise to the remarkable rate capabilities and extraordinary cycling stabilities for applications in fast and durable charge/discharge batteries. It is of great significance to incorporate Ti³⁺ into rutile TiO<inf>2</inf> to exhibit particular electrochemical characteristics triggering an effective way to improve the energy storage properties.